(599a) Experimental Study of Upper and Lower Flammability Limits of Syngas Mixtures

Authors: 
Fuller, C. C., Combustion Science & Engineering, Inc.
Gokulakrishnan, P., Combustion Science & Engineering, Inc.
Stephen, J., Combustion Science & Engineering, Inc.
Kim, S., Combustion Science & Engineering, Inc.
Introduction

Driven by the demand for alternative fuel sources, interest in coal-derived syngas and other high-hydrogen content fuels is growing. Given this demand, the need to better understand the ignition properties of syngas as well as the corresponding fire and safety hazards, including mixture flammability has become more prevalent. Currently, limited work exists in the literature regarding the lower (LFL) and upper (UFL) flammability limits of syngas and high-hydrogen fuels. The common industry method used to estimate LFL and UFL of fuel mixtures is the Le Chatelier mixing rule for chemical equilibria. It has been found that the Le Chatlelier mixing rule does not accurately predict the LFL and UFL for syngas and hydrogen mixtures. The objective of this study is to experimentally determine the LFL and UFL of syngas and high-hydrogen mixtures (H2, CO, CH4) using methods laid out in ASTM 618 and ASTM E918 and to compare those results to predictions made using the Le Chatelier mixing rule.

Experimental Program

Experiments are currently underway to measure the LFL and UFL of H2, CO, and CH4 and binary mixtures of varying concentrations to represent syngas and high-hydrogen fuel compositions. Experiments are being performed using two different experimental methods. This experimental program will include common data points that are examined using both methods.

Visual ignition in a 5L flask is being measured following the method laid out in ASTM 618 – Standard Test Method for Concentration Limits of Flammability of Chemicals. This method is being applied to determine the LFL values of CH4 and H2 at atmospheric pressure.

Ignition based on pressure rise is being measured following the method laid out in ASTM E918 – Standard Practice for Determining Limits of Flammability of Chemicals at Elevated Temperature and Pressure. This method is being applied to determine LFL and UFL values of binary mixtures of CH4, H2, and CO at atmospheric pressure.

Experimental results will be presented along with predictions made using the Le Chatelier mixing rule to determine its effectiveness. Any empirical models to improve syngas mixture flammability limits that are determined in this study will also be provided.